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Chitin was collected and extracted along different lifecycle stages of the Black Soldier Fly (BSF) (larvae, prepupae, pupae, flies, shedding & cocoons). The chitin content in the collected biomass ranged between 8% and 24%, with sheddings and cocoons being most rich in chitin. Purified chitin was subjected to a physicochemical evaluation based on FTIR, XRD, and TGA as well as a deacetylation step. The data indicated that BSF chitin was α-chitin with FTIR profiles matching closely to shrimp chitin and showing some differences compared to squid pen chitin (β-chitin). Small physicochemical differences were observed among the different BSF samples. Prepupae and cocoon chitin was more crystalline while chitin from larvae and sheddings had a lower thermal degradation temperature. In addition, sheddings were more difficult to purify. Further processing to chitosan showed that a deacetylation degree of 89% could be obtained for all samples after 3 h, although sheddings were found to be less reactive in the deacetylation process. Overall, the small differences in physicochemical properties that were detected between the BSF chitin samples did not prevent further processing of chitin to chitosan with the same degree of deacetylation via the same treatment.

Rhodomonas salina is a microalgal species, belonging to the cryptophytes, and is widely used as aquaculture feed because of its high nutritional profile and phycoerythrin content. This study investigated the effect of pH on the growth, biochemical composition, and taste of R. salina when cultivated on a semi-large scale under natural light conditions. Two tubular photobioreactors (200 L) were used for the cultivation of R. salina with sunlight as the only illumination source. Two different pH setpoints were applied, 7 and 8.5. Optimal temperature and nutrient conditions were applied, according to previous research findings. The results demonstrated that the productivity of R. salina was higher at pH 7, 0.06–0.14 gdry weight L−1 day−1, compared to pH 8.5, 0.03–0.12 gdry weight L−1 day−1. It was found that protein and total fatty acid concentrations were higher in the biomass that was produced at pH 8.5, 33.7% and 12.3% of dry weight, respectively, while at pH 7, the protein content was 31.9% and the total fatty acids 8.8% of dry weight. The phycoerythrin concentration, like protein, was higher at pH 8.5, 2.7% of dry weight, compared to pH 7, 1% of dry weight. The free amino acid and nucleotide profile of R. salina was affected by the pH, resulting in increased equivalent umami concentration at pH 7. For the sensory evaluation, an expert panel on algae flavors evaluated the effect of pH on the taste of R. salina, reporting that the biomass that was produced at pH 7 had more umami flavor than the biomass that was produced at pH 8.5, which was evaluated as more bitter.

This study aimed to map the nutritional profile and bioactivities of five microalgae that can be grown in Northwest Europe or areas with similar cultivation conditions. Next to the biochemical composition, the in vitro digestibility of carbohydrates, proteins, and lipids was studied for Chlamydomonas nivalis, Porphyridium purpureum, Chlorella vulgaris, Nannochloropsis gaditana, and Scenedesmus species biomass. These microalgae were also assessed for their ability to inhibit the angiotensin-1-converting enzyme (ACE-1, EC 3.4.15.1), which is known to play a role in the control of blood pressure in mammals. Large differences in organic matter solubility after digestion suggested that a cell disruption step is needed to unlock the majority of the nutrients from N. gaditana and Scenedesmus species biomass. Significant amounts of free glucose (16.4–25.5 g glucose/100 g dry algae) were detected after the digestion of C. nivalis, P. purpureum, and disrupted Scenedesmus. The fatty acid profiles showed major variations, with particularly high Ω-3 fatty acid levels found in N. gaditana (5.5 ± 0.5 g/100 g dry algae), while lipid digestibility ranged from 33.3 ± 6.5% (disrupted N. gaditana) to 67.1 ± 11.2% (P. purpureum). C. vulgaris and disrupted N. gaditana had the highest protein content (45–46% of dry matter), a nitrogen solubility after digestion of 65–71%, and the degree of protein hydrolysis was determined as 31% and 26%, respectively. Microalgae inhibited ACE-1 by 73.4–87.1% at physiologically relevant concentrations compared to a commercial control. These data can assist algae growers and processors in selecting the most suitable algae species for food or feed applications.

Insects are gaining interest as an alternative protein source for feed/food purposes. Although the lesser mealworm (LM) is commercially produced for human consumption, published data on its nutrient composition is scarce. This study reports on LM larvae reared on 18 different diets composed of side-streams to (1) determine the nutritional composition of the larvae and (2) study the effect of dietary changes on the larval nutrient composition. The LM larvae proved to be of good nutritional value with essential amino acids profiles comparable with that of beef and linoleic acid (C18:2) was the most dominant essential fatty acids in the larvae. The side-stream based diets varied on dry matter basis in protein (16&ndash, 34%) and lipid content (2&ndash, 19%). The nutrient content of the larvae reared on diets that supported good growth ranged between 37% and 49% of protein, 22% and 26% of lipid and 4% to 6% of chitin on dry matter basis. No significant correlations were identified between the larval protein or lipid content and that of the diet, but it was found between the diet nutrients and larval growth. Based on larval growth data and economic considerations, diets composed of wheat middlings with a 10&ndash, 15% inclusion of rapeseed meal were identified as suitable feed for LM. Highest larval yields were obtained with diets containing 15&ndash, 22% of proteins and 5&ndash, 10% of lipids.

Protein hydrolysates from lesser mealworm (Alphitobius diaperinus, LM) were obtained by enzymatic hydrolysis with protease from Bacillus licheniformis. A preliminary test performed for five hours of hydrolysis generated an insect protein hydrolysate with 15% of degree of hydrolysis (DH), optimum solubility property and oil holding capacity, but emulsifying and foaming ability were completely impaired. In order to investigate the potential implication of DH on techno-functional properties, a set of protein hydrolysates with a different DH was obtained by sub-sampling at different time points during three hours of enzymatic hydrolysis process. An increase in DH% had positive effects on the solubility property and oil holding ability, while a reduced emulsifying ability was observed up to five hours of hydrolysis. These results demonstrated that the enzymatic hydrolysis, if performed under controlled conditions and not for a long period, represents a valid method to extract high quality protein from insects with tailored techno-functionality, in order to produce tailored ingredients for feed and food purpose.

The impact of a silica coating on the degradation potential of nanoscale zerovalent iron (nZVI) particles toward a mixture of chlorinated ethylenes is presented. The newly employed stabilization method for nZVI, based on silica deposition from saturated sodium silicate water glass, produces nZVI particles with a similar reactivity as non-stabilized particles. Moreover the removal rate constant kM of trichloroethylene (0.1740 L g−1 d−1 Fe0) and cis-dichloroethylene (0.1045 L g−1 d−1Fe0) was significantly improved (almost by a factor of 2) for stabilized nZVI. X-ray photoelectron spectroscopy (XPS) and Wavelength Dispersive X-ray Fluorescence (WDXRF) analyzes revealed a high durability of silica coating and the coating left at least half of nZVI surface silica free for reaction for more than 5 weeks. The silica coating did not affect the surface composition of silica coated nZVI which was confirmed by the very similar distribution of degradation products and corrosion products (Fe3O4, FeOOH) as was found for non-coated nanoparticles. An enhanced reactivity supplemented with a stable corrosion properties indicates that silica coated nZVI has potential as an efficient remediation agent toward chlorinated ethylenes.

The reactivity and apparent corrosion rate of newly produced boron-alloyed microscale zerovalent iron (mZVI) particles toward a variety of chlorinated aliphatic hydrocarbons (CAHs) were assessed in laboratory-scale batch reactors. For comparison, commercially available nanoscale zerovalent irons (nZVIs) were also included in the study. Based on mass normalized ( k M ) pseudo first-order degradation rate constants, the reactivity of boron-alloyed mZVIs appeared to be one order of magnitude lower than most reactive nZVI. However, specific surface area normalized reaction rate constants ( k SA ) were 1–2 orders of magnitude higher than for nZVIs showing that boron-alloyed mZVIs can compete with nZVIs. The high reactivity of boron-alloyed mZVIs was attributed to (1) the prevented iron surface passivation during anaerobic corrosion due to the simultaneous iron and boron dissolution kinetics preventing the formation of insoluble oxidized iron species, (2) the involvement of boron in facilitating electron transfer by inducing β-elimination followed by hydrogenation to ethane and/or (3) involvement of boron in improved particle size reduction during milling process leading to increased active surface areas of the particles. Results of this study suggest that boron-alloyed mZVIs could be an efficient alternative to nZVIs for in situ groundwater remediation of different CAHs in terms of their reactivity and apparent corrosion rate.

It is often impossible in practice to process micro-algae immediately after their cultivation and harvest. This study, therefore, aimed to identify appropriate storage conditions for the wet preservation of Porphyridium purpureum. Algae were stored either as a concentrate or as a dilute culture at 4 &deg, C, 8 &deg, C, or 20 &deg, C for 14 days and their quality was monitored. Concentrate storage tended to result in higher microbial numbers than dilute culture storage and clearly led to higher concentrations of malodorous organic acids. Butyric and isovaleric acid concentrations were about two orders of magnitude larger than their odor threshold values after 14 days of concentrate storage at 20 &deg, C. Average B-phycoeryhrin (B-PE) levels were slightly higher after concentrate storage (2.5 &plusmn, 0.2 g B-PE/100 g organic matter) than after dilute culture storage (2.2 &plusmn, 0.5 g B-PE/100 g organic matter), probably due to respiration losses of other organic compounds in the first case. Significant amounts of organic matter got lost during concentrate storage (4&ndash, 35%) as a result of carbohydrate degradation. The main restriction of concentrate storage was the rapid viscosity increase and formation of a weak gel structure complicating the later processing of the concentrates. These findings are highly relevant for P. purpureum cultivators and processors who have to store Porphyridium suspensions, even on a term of one day or less.

Impacts of subsurface biogeochemical processes over time have always been a concern for the long-term performance of zero valent iron (Fe(0))-based permeable reactive barriers (PRBs). To evaluate the biogeochemical impacts, laboratory experiments were performed using flow-through glass columns for 210 days at controlled temperature (20 °C). Two different particle sizes of Fe(0) were used in the columns, and to simulate indigenous microbial activity, extra carbon source was provided in the two columns (biotic columns) and the remaining two columns were kept abiotic using gamma radiations. Heavy metals (Zn, As) were removed efficiently in all the columns, and no exhaustion of treatment capability or clogging was observed during our experimental duration. Newly formed Fe mineral phases and precipitates were characterized using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), and micro-XRF techniques in solid phase at the end of the experiment. In addition, 16S rRNA gene extraction was used for microbial community identification in biotic columns. During the incubation, microbial population shifted in favor of Desulfosporosinus species (sulfate-reducing bacteria) from initial dominance of Acidithiobacillus ferrooxidans in sediments. Dominant mineral phases detected in biotic columns were mackinawite (FeS) and sulfate green rust, while in abiotic columns, magnetite/maghemite phases were more prevalent.

Insects are considered a promising alternative protein source for food and feed, but contain significant amounts of chitin, often undesirable due to indigestibility, disagreeable texture and negative effect on nutrients intake. Fractionation strategies are thus increasingly being applied to isolate and valorize chitin separately. The analysis of chitin generally requires an intensive pretreatment to remove impurities, and derivatization to generate sufficient detector response. In this work, a liquid chromatography method, without pretreatment nor derivatization, was developed for the simultaneous determination of chitin content and degree of acetylation in non-purified samples of black soldier fly (BSF) larvae. The method is found to be more suitable, compared to traditional methods, for assessing high degrees of acetylation. For the first time, the degree of acetylation of BSF chitin (81 ± 2%) is reported. Additionally, the chitin content of BSF soft tissues is estimated at approximately 20% of the total chitin content (8.5 ± 0.1%).

Algal lipids have gained wide interest in various applications ranging from biofuels to nutraceuticals. Given their complex nature composed of different lipid classes, a deep knowledge between extraction conditions and lipid characteristics is essential. In this paper, we investigated the influence of different pretreatments on lipid extraction with supercritical CO2 by a lipidomic approach. Pretreatment was found to double the total extraction yield, thereby reaching 23.1 wt.% comparable to the 26.9 wt.% obtained with chloroform/methanol. An increase in acylglycerides was concurrently observed, together with a nearly doubling of free fatty acids indicative of partial hydrolysis. Moreover, an alteration in the distribution of glyco- and phospholipids was noted, especially promoting digalactosyldiglycerides and phosphatidylcholine as compared to monogalactosyldiglycerides and phosphatidylglycerol. At optimized conditions, supercritical CO2 extraction provided a lipid extract richer in neutral lipids and poorer in phospholipids as compared to chloroform/methanol, though with a very similar fatty acid distribution within each lipid class.

The release of fine zerovalent iron (ZVI) particles in the environment after being introduced for in-situ treatment of compounds like chlorinated aliphatic hydrocarbons (CAHs) may raise questions toward environmental safety, especially for nanoscale materials. Classical single-species ecotoxicity tests do focus on aerobic conditions and are only relevant for the scenario when ZVI-particles reach surface water. Herein, we present an alternative approach where a CAH-degrading mixed bacterial culture was used as test-organisms relevant for the anaerobic subsurface. The impact of different ZVI particles on the bacterial culture was evaluated mainly by quantifying ATP, a reporter molecule giving a general indication of the microbial activity. These lab-scale batch tests were performed in liquid medium, without protecting and buffering aquifer material, as such representing worst-case scenario. The activity of the bacterial culture was negatively influenced by nanoscale zerovalent iron at doses as low as 0.05 g L−1. On the other hand, concentrations up to 2 g L−1 of several different types of microscale zerovalent iron (mZVI) particles stimulated the activity. However, very high doses of 15–30 g L−1 of mZVI showed an inhibiting effect on the bacterial community. Negative effects of ZVIs were confirmed by H2 accumulation in the batch reactors and the absence of lactate consumption. Observed inhibition also corresponded to a pH increase above 7.5, explicable by ZVI corrosion that was found to be dose-dependent. The obtained results suggest that low doses of mZVIs will not show severe inhibition effects on the microbial community once used for in-situ treatment of CAHs.

Microalgae harvesting is a major challenge because microalgal cells are small and carry a negative surface charge and biomass concentration in cultures is relatively low. The microalgal biomass (0.05%, w/w) needs to be concentrated to a paste with 15%–25% water content. This dewatering process is ideally performed in two stages, including a first preconcentration step in combination with a second dewatering step. Microalgae are a very heterogeneous group of organisms differing in size and shape and culture conditions. Applications of microalgal biomass range from low-value (biofuels) to high-value applications (nutraceuticals). It is therefore likely that the optimal harvesting technology differs between species, culture conditions, or the final application of the biomass. Harvesting should not cause contamination of the biomass or influence biomass quality. Finally, water recycling to reduce the water footprint is an important aspect to include into the harvesting process. This chapter gives an overview of several harvesting process options with the focus on their strengths and highlighting the aforementioned aspects. ispartof: Microalgae-based Biofuels and Bioproducts pages:113-132 ispartof: Woodhead Publishing Series in Energy pages:113-132 status: published

In this chapter, cell disruption techniques are reviewed as a function of the (future) industrial algae biorefinery. A variety of techniques and recent developments are discussed based on their effectiveness, product quality, and cost efficiency. Effectiveness (i.e, disruption efficiency in function of energy and time) unfortunately is often countered by poor product quality, and currently used industrial methods are generally energy intensive. Recent developments might tackle these issues and enhance the economics. Chemical techniques are often effective but can lead to impurities in the final product, which can be avoided by immobilizing chemical agents. Alternatively, several pressurized methods are promising because of high product quality and relatively low energy consumption. The latter can even be decreased significantly based on recent advances, which also counts for well-established techniques undergoing process optimization. The field, however, remains challenging to increase effectiveness and product quality to decrease downstream process steps and overall costs.

cis -1,2-Dichloroethene ( cis -DCE) and trichloroethene (TCE) are persistent, toxic and mobile pollutants in groundwater systems. They are both conducive to reductive dehalogenation and to oxidation by permanganate. In this study, the potential of dual element (C, Cl) compound specific isotope analyses (CSIA) for distinguishing between chemical oxidation and anaerobic reductive dechlorination of cis -DCE and TCE was investigated. Well-controlled cis -DCE degradation batch tests gave similar carbon isotope enrichment factors e C (‰), but starkly contrasting dual element isotope slopes Δ δ 13 C/Δ δ 37 Cl for permanganate oxidation (e C = − 26‰ ± 6‰, Δ δ 13 C/Δ δ 37 Cl ≈ − 125 ± 47) compared to reductive dechlorination (e C = − 18‰ ± 4‰, Δ δ 13 C/Δ δ 37 Cl ≈ 4.5 ± 3.4). The difference can be tracked down to distinctly different chlorine isotope fractionation: an inverse isotope effect during chemical oxidation (e Cl = + 0.2‰ ± 0.1‰) compared to a large normal isotope effect in reductive dechlorination (e Cl = − 3.3‰ ± 0.9‰) ( p ≪ 0.05). A similar trend was observed for TCE. The dual isotope approach was evaluated in the field before and up to 443 days after a pilot scale permanganate injection in the subsurface. Our study indicates, for the first time, the potential of the dual element isotope approach for distinguishing cis -DCE (and TCE) concentration drops caused by dilution, oxidation by permanganate and reductive dechlorination both at laboratory and field scale.

In this study, the aging behavior of microscale zerovalent iron (mZVI) particles was investigated by quantifying the hydrogen gas generated by anaerobic mZVI corrosion in batch degradation experiments. Granular iron and nanoscale zerovalent iron (nZVI) particles were included in this study as controls. Firstly, experiments in liquid medium (without aquifer material) were performed and revealed that mZV1 particles have approximately a 10-30 times lower corrosion rate than nZVI particles. A good correlation was found between surface area normalized corrosion rate (R-SA) and reaction rate constants (K-SA) of PCE, TCE, cDCE and 1,1,1-TCA. Generally, particles with higher degradation rates also have faster corrosion rates, but exceptions do exists. In a second phase, the hydrogen evolution was also monitored during batch tests in the presence of aquifer material and real groundwater. A 4-9 times higher corrosion rate of mZV1 particles was observed under the natural environment in comparison with the aquifer free artificial condition, which can be attributed to the low pH of the aquifer and its buffer capacity. A corrosion model was calibrated on the batch experiments to take into account the inhibitory effects of the corrosion products (dissolved iron, hydrogen and OH-) on the iron corrosion rate. (C) 2014 Elsevier B.V. All rights reserved.

In this study we investigate the model uncertainties involved in predicting long-term permeable reactive barrier (PRB) remediation efficiency based on a lab-scale column experiment under accelerated flow conditions. A PRB consisting of 20% iron and 80% sand was simulated in a laboratory-scale column and contaminated groundwater was pumped into the column for approximately 1 year at an average groundwater velocity of 3.7E - 1 m d(-1). Dissolved contaminants (PCE. TCE, cis-DCE, trans-DCE and VC) and inorganic (Ca2+, Fe2+, TIC and pH) concentrations were measured in groundwater sampled at different times and at eight different distances along the column. These measurements were used to calibrate a multi-component reactive transport model, which subsequently provided predictions of long-term PRB efficiency under reduced flow conditions (i.e., groundwater velocity of 1.4E -3 m d(-1)), representative of a field site of interest in this study. Iron reactive surface reduction due to mineral precipitation and iron dissolution was simulated using four different models. All models were able to reasonably well reproduce the column experiment measurements, whereas the extrapolated long-term efficiency under different flow rates was significantly different between the different models. These results highlight significant model uncertainties associated with extrapolating long-term PRB performance based on lab-scale column experiments. These uncertainties should be accounted for at the PRB design phase, and may be reduced by independent experiments and field observations aimed at a better understanding of reactive surface deactivation mechanisms in iron PRBs. (C) 2012 Elsevier B.V. All rights reserved.

Microscale zerovalent iron (mZVI) reduces chlorinated aliphatic hydrocarbons (CAHs) to harmless compounds, but the sedimentation of the mZVI particles in the injection fluid limits the injectability of the particles during field applications. In this study, mZVI particles in suspension were stabilized by green polymer guar gum, which had a positive impact on mZVI stability, but decreased the reactivity of the particles towards CAHs by 1 to 8 times. Guar gum (GG) was found to adsorb onto the mZVI surface, inhibiting contact between the chlorinated compounds and the reactive iron surface. Indications were found for intermolecular hydrogen bonding between mZVI and the guar gum. Subsequent addition of commercially available enzymes resulted in the cleavage of the polysaccharide guar gum into lower molecular fragments, but not in improved reactivity. The reactivity recovery of guar gum coupled mZVI was recovered after intensive rinsing of the iron particles, removing the guar gum fragments from the particles. Overall, this study shows that CAHs can be treated efficiently by guar gum stabilized mZVI after reactivation by means of enzymatic breakdown and rinsing. (C) 2012 Elsevier B.V. All rights reserved.

The widespread use of methyl tertiary butyl ether (MTBE) as an additive in gasoline has resulted in serious soil and groundwater pollution. To tackle MTBE contamination in groundwater, bioremediation is considered a cost-effective and energy-efficient option. The design of an efficient, reliable and reproducible bioremediation strategy requires a thorough understanding of the (microbial) degradation kinetics of both MTBE and tertiary butyl alcohol (TBA), that is, the main intermediate during bioremediation of MTBE. To assist the design procedure, this research focuses on building a mathematical model to describe MTBE/TBA degradation kinetics by a bacterial consortium, that is, the VITO M-consortium. For the presented case study, the information obtained from experimental data is combined with knowledge regarding the biodegradation reactions in order to obtain a low-complexity, accurate mathematical model. The resulting model accurately describes MTBE/TBA degradation and has successfully been validated on ...

The Monkstown zero-valent iron permeable reactive barrier (ZVI PRB), Europe's oldest commercially-installed ZVI PRB, had been treating trichloroethene (TCE) contaminated groundwater for about 10 years on the Nortel Network site in Northern Ireland when cores from the reactive zone were collected in December, 2006. Groundwater data from 2001-2006 indicated that TCE is still being remediated to below detection limits as the contaminated groundwater flows through the PRB. Ca and Fe carbonates, crystalline and amorphous Fe sulfides, and Fe (hydr)oxides have precipitated in the granular ZVI material in the PRB. The greatest variety of minerals is associated with a approximately 1-2 cm thick, slightly cemented crust on top (up-gradient influent entrance) of the ZVI section of the PRB and also with the discontinuous cemented ZVI material ( approximately 23 cm thick) directly below it. The greatest presence of microbial communities also occurred in the up-gradient influent portion of the PRB compared to its down-gradient effluent section, with the latter possibly due to less favorable conditions (i.e., high pH, low oxygen) for microbial growth. The ZVI filings in the down-gradient effluent section of the PRB have a projected life span of >10 years compared with ZVI filings from the continuous to discontinuous cemented up-gradient ZVI section (upper approximately 25 cm) of the PRB, which may have a life span of only approximately 2-5 more years. Supporting Information from applied, multi-tracer testing indicated that restricted groundwater flow is occurring in the upper approximately 25 cm of the ZVI section and preferential pathways have also formed in this PRB over its 10 years of operation.

A 2-year-old pilot-scale zerovalent iron (Fe-0)-permeable reactive barrier, treating groundwater contaminated with tetrachloroethylene and trichloroethylene, was microbially characterized using DNA-based polymerase chain reaction-DGGE (denaturing gradient gel electrophoresis) analysis. In situ mesocosm systems positioned in monitoring wells at different locations in the pilot-scale system allowed core sampling as a function of time without disturbing the barrier performance. Mesocosms were harvested from each location after 3, 7, and 23 months of operation and revealed the presence of Eubacteria, Archaea, and different functional groups of bacteria, which might affect iron barrier performance, including sulfate-reducing bacteria, iron(III)-reducing bacteria, denitrifying bacteria, and methanogens. DGGE fingerprints of the eubacterial 16S rDNA polymerase chain reaction amplification products clearly indicated different community structures in the iron material compared with the aquifer material. Gene sequencing of two dominant bands observed in samples collected from the iron barrier showed a maximum sequence similarity of 97% and 94% with a Firmicutes bacterium and an iron(III)-reducing bacterium enrichment culture clone, respectively. Results indicate that Fe-0 had a profound impact on the microbial community composition, most likely by decreasing the redox potential and increasing the pH of the groundwater.

Methyl tertiary butyl ether or MTBE is often used as an additive in gasoline to boost the octane rating and to promote more efficient combustion of the gasoline. This widespread use of MTBE has resulted in serious soil and groundwater pollution. To tackle MTBE contamination in groundwater, bioremediation is considered a cost-effective and energy-efficient option. The design of an efficient, reliable and reproducible bioremediation strategy requires a thorough understanding of the (microbial) degradation kinetics of both MTBE and TBA (tertiary butyl alcohol), i.e., the main intermediate during bioremediation of MTBE. To assist the design procedure, this research focuses on building a low complexity, yet accurate mathematical model to describe MTBE/TBA degradation kinetics by a bacterial consortium, i.e., the VITO M-consortium. The resulting model provides an accurate description of MTBE/TBA degradation and has successfully been validated on independent experimental data. Since the model is of the mass balance type, it can easily be extended to other types of operation by defining the transport terms of the new system. This makes the model a very useful tool in the design procedure for large scale bioremediation strategies. Furthermore, the model provides insight in the MTBE/TBA degradation kinetics and biodegradation mechanisms by hypothesis testing.

This study describes a laboratory-scale multifunctional permeable reactive barrier (multibarrier) for the removal of ammonium (NH4+: 313 +/- 51 mg N L(-1)), adsorbable organic halogens (AOX: 0.71 +/- 0.25 mg Cl L(-1)), chemical oxygen demand (COD: 389 +/- 36 mg L(-1)), and toxicity from leachate originating from a 40-year-old Belgian landfill. The complexity of the contamination required a sequential setup combining different reactive materials and removal processes. All target contaminants could be removed to levels below the regulatory discharge limits. Ammonium was efficiently removed in a first microbial nitrification compartment, which was equipped with diffusive oxygen emitters to ensure a sufficient oxygen supply. Ammonium was mainly oxidized to nitrite and to a lesser extent to nitrate, with an average mass recovery of 96%. Remaining ammonium concentrations could be further removed by ion exchange in a second compartment filled with clinoptilolite, exhibiting a total ammonium removal capacity of 46.7 mg N per g of clinoptilolite. Athird microbial denitrification compartment fed with sodium butyrate as a carbon source, was used to remove nitrate and nitrite formed in the first compartment. Maximum nitrification and denitrification rates at 12 degrees C indicated that hydraulic retention times of approximately 62 h and approximately 32 h were required in the columns to remove 400 mg N L(-1) by nitrification and denitrification, respectively. Leachate toxicity decreased to background levelstogetherwiththe removal of ammonium and its oxidation products. AOX and COD were efficiently removed by sorption in an additional compartment filled with granular activated carbon.

The injection of microscale zerovalent iron (mZVI) particles for groundwater remediation has received much interest in recent years. However, to date, monitoring of mZVI particle injection is based on chemical analysis of groundwater and soil samples and thus might be limited in its spatiotemporal resolution. To overcome this deficiency, in this study, we investigate the application of complex electrical conductivity imaging, a geophysical method, to monitor the high-pressure injection of mZVI in a field-scale application. The resulting electrical images revealed an increase in the induced electrical polarization (∼20%), upon delivery of ZVI into the targeted area, due to the accumulation of metallic surfaces at which the polarization takes place. Furthermore, larger changes (>50%) occurred in shallow sediments, a few meters away from the injection, suggesting the migration of particles through preferential flowpaths. Correlation of the electrical response and geochemical data, in particular the analysis of recovered cores from drilling after the injection, confirmed the migration of particles (and stabilizing solution) to shallow areas through fractures formed during the injection. Hence, our results demonstrate the suitability of the complex conductivity imaging method to monitor the transport of mZVI during subsurface amendment in quasi real-time.

International audience; We conducted a series of flow-through column experiments using aquifer sediment treated with zero valent iron (Fe-0) with or without active microbial sulfate reduction. The aim of this study was to investigate the stability of Zn removed by Fe-0 and impact of sulfate reducing bacteria (SRB). The leaching of Zn was assessed by flushing the aquifer in vertical glass columns with groundwater that was pre-treated with mixture of gases to simulate natural changes (pH and ORP) in subsurface environment (N-2 + CO2 for pH and N-2 + O-2 for ORP) along with a control (N-2 flushed). Zinc removed synergistically by Fe and SRBs was found to be more stable and did not leach from the aquifer sediment with pH or redox changes. We also observed that the Zn leaching in the aquifer treated only with Fe was more influenced by change in redox than by pH changes. These results were also confirmed by sequential metal extractions and scanning electron microscopy observations in the aquifer sediments. Mineral phases were predicted using geochemical modeling tool CHESS confirming that the metal removed in Fe-o + SRB conditions formed more stable precipitates and did not show any signs of leaching back to groundwater upon change in pH and redox conditions. (C) 2014 Elsevier B.V. All rights reserved.

In this study a numerical groundwater reactive transport model of a shallow groundwater aquifer contaminated with volatile organic compounds is developed. In addition to advective-dispersive transport, the model includes contaminant release from source areas, natural attenuation, abiotic degradation by a permeable reactive barrier at the site, and dilution by infiltrating rain. Aquifer heterogeneity is parameterized using pilot points for hydraulic conductivity, specific yield and groundwater recharge. A methodology is developed and applied to estimate the large number of parameters from the limited data at the field site (groundwater levels, groundwater concentrations of multiple chemical species, point-scale measurements of soil hydraulic conductivity, and lab-scale derived information on chemical and biochemical reactions). The proposed methodology relies on pilot point parameterization of hydraulic parameters and groundwater recharge, a regularization procedure to reconcile the large number of spatially distributed model parameters with the limited field data, a step-wise approach for integrating the different data sets into the model, and high performance computing. The methodology was proven to be effective in reproducing multiple contaminant plumes and in reducing the prior parameter uncertainty of hydraulic conductivity and groundwater recharge. Our results further indicate that contaminant transport predictions are strongly affected by the choice of the groundwater recharge model and flow parameters should be identified using both head and concentration measurements. (C) 2014 Elsevier B.V. All rights reserved.

The combined removal of chlorinated ethenes and heavy metals from a simulated groundwater matrix by zerovalent iron (ZVI) was investigated. In batch, Ni (5-100 mg L(-1)) enhanced trichloroethene (TCE, 10 mg L(-1)) reduction by ZVI (100 g L(-1)) due to catalytic hydrodechlorination by bimetallic Fe0/Ni0. Cr(VI) or Zn (5-100 mg L(-1)) lowered TCE degradation rates by a factor of 2 to 13. Cr(VI) (100 mg L(-1)) in combination with Zn or Ni (50-100 mg L(-1)) inhibited TCE degradation. Addition of 20% H2(g) in the headspace, or of Zn (50-100 mg L(-1)), enhanced TCE removal in the presence of Ni and Cr(VI). Sorption of Zn to ZVI alleviated the Cr(VI) induced inhibition of bimetallic Fe0/Ni0 apparently due to release of protons necessary for TCE hydrodechlorination. In continuous ZVI columns treating tetrachloroethene (PCE, 1-2 mg L(-1)) and TCE (10 mg L(-1)), and a mixture of the metals Cr(VI), Zn(II), and Ni(II) (5 mg (L-1)), the PCE removal efficiency decreased from 100% to 90% in columns operated without heavy metals. The PCE degradation efficiency remained above 99% in columns receiving heavy metals as long as Ni was present. The findings of this study indicate the feasibility and limitations of the combined treatment of mixtures of organic and inorganic pollutants by ZVI.

An in situ mesocosm system was designed to monitor the in situ dynamics of the microbial community in polluted aquifers. The mesocosm system consists of a permeable membrane pocket filled with aquifer material and placed within a polypropylene holder, which is inserted below groundwater level in a monitoring well. After a specific time period, the microcosm is recovered from the well and its bacterial community is analyzed. Using this system, we examined the effect of benzene, toluene, ethylbenzene, and xylene (BTEX) contamination on the response of an aquifer bacterial community by denaturing gradient gel electrophoresis analysis of PCR-amplified 16S rRNA genes and PCR detection of BTEX degradation genes. Mesocosms were filled with nonsterile or sterile aquifer material derived from an uncontaminated area and positioned in a well located in either the uncontaminated area or a nearby contaminated area. In the contaminated area, the bacterial community in the microcosms rapidly evolved into a stable community identical to that in the adjacent aquifer but different from that in the uncontaminated area. At the contaminated location, bacteria with tmoA - and xylM/xylE1 -like BTEX catabolic genotypes colonized the aquifer, while at the uncontaminated location only tmoA -like genotypes were detected. The communities in the mesocosms and in the aquifer adjacent to the wells in the contaminated area consisted mainly of Proteobacteria . At the uncontaminated location, Actinobacteria and Proteobacteria were found. Our results indicate that communities with long-term stability in their structures follow the contamination plume and rapidly colonize downstream areas upon contamination.

The Sphingomonas genus hosts many interesting pollutant-degrading strains. Sphingomonas sp. EPA505 is the best studied polycyclic aromatic hydrocarbon (PAH)-degrading Sphingomonas strain. Based on 16S rRNA gene sequence analysis, Sphingomonas sp. strain EPA505 forms a separate branch in the Sphingomonas phylogenetic tree grouping exclusively PAH-degrading isolates. For specific PCR detection and monitoring of Sphingomonas sp. EPA505 and related strains in PAH-contaminated soils, a new 16S rRNA gene-based primer set was designed. The new primer set was shown to be highly selective for Sphingomonas sp. strain EPA505 as it only amplified DNA from strain EPA505 and not from other tested Sphingomonas strains or soil bacteria not belonging to the Sphingomonas genus. Using DNA extracts of a variety of inoculated PAH-contaminated soils, the primer pair was able to detect EPA505 in concentrations as low as 10(2) cells per gram of soil. Applying the new primer set, 16S rRNA gene fragments which were 99-100% similar to the corresponding gene of strain EPA505 were amplified from four of five PAH-contaminated soils. On the other hand, no PCR products were obtained from any of five tested uncontaminated soils. The preferential presence of EPA505 related Sphingomonas strains in PAH-contaminated soils with very different contamination profiles and different origin suggests an important role of this type of Sphingomonas in the natural Sphingomonas community colonizing PAH-contaminated sites.

Fast-growing mycobacteria are considered essential members of the polycyclic aromatic hydrocarbons (PAH) degrading bacterial community in PAH-contaminated soils. To study the natural role and diversity of the Mycobacterium community in contaminated soils, a culture-independent fingerprinting method based on PCR combined with denaturing gradient gel electrophoresis (DGGE) was developed. New PCR primers were selected which specifically targeted the 16S rRNA genes of fast-growing mycobacteria, and single-band DGGE profiles of amplicons were obtained for most Mycobacterium strains tested. Strains belonging to the same species revealed identical DGGE fingerprints, and in most cases, but not all, these fingerprints were typical for one species, allowing partial differentiation between species in a Mycobacterium community. Mycobacterium strains inoculated in soil were detected with a detection limit of 10(6) CFU g(-1) of soil using the new primer set as such, or approximately 10(2) CFU g(-1) in a nested PCR approach combining eubacterial and the Mycobacterium specific primers. Using the PCR-DGGE method, different species could be individually recognized in a mixed Mycobacterium community. This approach was used to rapidly assess the Mycobacterium community structure of several PAH-contaminated soils of diverse origin with different overall contamination profiles, pollution concentrations and chemical-physical soil characteristics. In the non-contaminated soil, most of the recovered 16S rRNA gene sequence did not match with previous described PAH-degrading Mycobacterium strains. In most PAH-contaminated soils, mycobacteria were detected which were closely related to fast-growing species such as Mycobacterium frederiksbergense and Mycobacterium austroafricanum, species that are known to include strains with PAH-degrading capacities. Interestingly, 16S rRNA genes related to M. tusciae sequences, a Mycobacterium species so far not reported in relation to biodegradation of PAHs, were detected in all contaminated soils. (C) 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.

Chlorinated aliphatic hydrocarbons are common groundwater contaminants. One possible remediation option is in-situ reductive dechlorination by zero-valent iron, either by direct injection or as reactive barriers. Chlorinated ethenes (tetrachloroethene: PCE; trichloroethene: TCE) have received extensive attention in this context. However, another common groundwater pollutant, 1,1,1-trichlorethane (TCA), has attracted much less attention. We studied TCA reduction by three types of granular zero-valent irons in a series of batch experiments using polluted groundwater, with and without added aquifer material. Two types of iron were able to reduce TCA completely with no daughter product concentration increases (1,1-dichloroethane: DCA; chloroethane: CA). One type of iron showed slower reduction, with intermediate rise of DCA and CA concentrations. When evaluating the formation of daughter products, the tests on the groundwater alone showed different results than the groundwater plus aquifer batches: DCA did not temporarily accumulate in the batches with added aquifer material, contrary to the batches without added aquifer material. 1,1-dichloroethene (DCE, also present in the groundwater as an abiotic degradation product of TCA) was also reduced slower in the batches without added aquifer material than in the batches with aquifer material. Redox potentials gradually decreased to low values in batches with aquifer material without iron, while the batches with groundwater alone maintained a constant higher redox potential. Either adsorption processes or microbiological activity in the samples could explain these phenomena. Polymerase Chain Reaction (PCR: a targeted gene probe technique) for chlorinated aliphatic compound (CAH)-degrading bacteria confirmed the presence of Dehalococcoides sp. (chloroethene-degraders) but was negative for Desulfobacterium autotrophicum (a known co-metabolic TCA degrader). DCA reduction was rate determining: first-order half-lives of 300-350 h were observed. TCA was fully removed within hours. CA is resistant to reduction by zero-valent iron but it is known to hydrolyze easily. Since CA did not accumulate in our batches, it may have disappeared by the latter mechanism or it may not have formed as a major daughter product.

Bacterial strains of the genus Sphingomonas are often isolated from contaminated soils for their ability to use polycyclic aromatic hydrocarbons (PAH) as the sole source of carbon and energy. The direct detection of Sphingomonas strains in contaminated soils, either indigenous or inoculated, is, as such, of interest for bioremediation purposes. In this study, a culture-independent PCR-based detection method using specific primers targeting the Sphingomonas 16S rRNA gene combined with denaturing gradient gel electrophoresis (DGGE) was developed to assess Sphingomonas diversity in PAH-contaminated soils. PCR using the new primer pair on a set of template DNAs of different bacterial genera showed that the method was selective for bacteria belonging to the family Sphingomonadaceae . Single-band DGGE profiles were obtained for most Sphingomonas strains tested. Strains belonging to the same species had identical DGGE fingerprints, and in most cases, these fingerprints were typical for one species. Inoculated strains could be detected at a cell concentration of 10 4 CFU g of soil −1 . The analysis of Sphingomonas population structures of several PAH-contaminated soils by the new PCR-DGGE method revealed that soils containing the highest phenanthrene concentrations showed the lowest Sphingomonas diversity. Sequence analysis of cloned PCR products amplified from soil DNA revealed new 16S rRNA gene Sphingomonas sequences significantly different from sequences from known cultivated isolates (i.e., sequences from environmental clones grouped phylogenetically with other environmental clone sequences available on the web and that possibly originated from several potential new species). In conclusion, the newly designed Sphingomonas -specific PCR-DGGE detection technique successfully analyzed the Sphingomonas communities from polluted soils at the species level and revealed different Sphingomonas members not previously detected by culture-dependent detection techniques.

The paper reports a pilot injection test of microsized zerovalent iron (mZVI) dispersed in a guar gum shear thinning solution. The test was performed in the framework of the EU research project AQUAREHAB in a site in Belgium contaminated by chlorinated aliphatic hydrocarbons (CAHs). The field application was aimed to overcome those critical aspects which hinder mZVI field injection, mainly due to the colloidal instability of ZVI-based suspensions. The iron slurry properties (iron particles size and concentration, polymeric stabilizer type and concentration, slurry viscosity) were designed in the laboratory based on several tests (reactivity tests towards contaminants, sedimentation tests and rheological measurements). The particles were delivered into the aquifer through an injection well specifically designed for controlled-pressure delivery (approximately 10 bars). The well characteristics and the critical pressure of the aquifer (i.e. the injection pressure above which fracturing occurs) were assessed via two innovative injection step rate tests, one performed with water and the other one with guar gum. Based on laboratory and field preliminary tests, a flow regime at the threshold between permeation and preferential flow was selected for mZVI delivery, as a compromise between the desired homogeneous distribution of the mZVI around the injection point (ensured by permeation flow) and the fast and effective injection of the slurry (guaranteed by high discharge rates and injection pressure, resulting in the generation of preferential flow paths). A monitoring setup was designed and installed for the real-time monitoring of relevant parameters during injection, and for a fast determination of the spatial mZVI distribution after injection via non-invasive magnetic susceptibility measurements.

A column study was performed under in situ conditions to evaluate to which extend the inactivation of the microscale zerovalent iron (mZVI) by guar gum occurs under continuous flow conditions. Five aquifer containing columns were set up under different conditions. Efficient removal of trichloroethene was observed for the column amended by mZVI. Stabilization of the mZVI with guar gum led to slightly reduced activity. More reduced reactivity was observed in the poisoned column containing guar gum stabilized mZVI. This confirms that soil microorganisms can degrade guar gum and that subsequent removal of the oligosaccharides by the groundwater flow (flushing effect) can reactivate the mZVI. After more than six months of continuous operation the columns were dismantled. DNA-based qPCR analysis revealed that mZVI does not significantly affect the bacterial community, while guar gum stabilized mZVI particles can even induce bacterial growth. Overall, this study suggests that the temporarily decreased mZVI reactivity due to guar gum, has a rather limited impact on the performance of in situ reactive zones. The presence of guar gum slightly reduced the reactivity of iron, but also slowed down the iron corrosion rate which prolongs the life time of reactive zone (C) 2013 Elsevier B.V. All rights reserved.

A pilot injection test with guar gum stabilized microscale zerovalent iron (mZVI) particles was performed at test site V (Belgium) where different chlorinated aliphatic hydrocarbons (CAHs) were present as pollutants in the subsurface. One hundred kilograms of 56 pm-diameter mZVI (similar to 70 g L-1) was suspended in 1.5 m(3) of guar gum (similar to 7 g L-1) solution and injected into the test area. In order to deliver the guar gum stabilized mZVI slurry, one direct push bottom-up injection (Geoprobe) was performed with injections at 5 depths between 10.5 and 8.5 m bgs. The direct push technique was preferred above others (e.g. injection at low flow rate via screened wells) because of the limited hydraulic conductivity of the aquifer, and to the large size of the mZVI particles. A final heterogeneous distribution of the mZVI in the porous medium was observed explicable by preferential flow paths created during the high pressure injection. The maximum observed delivery distance was 2.5 m. A significant decrease in 1,1,1-TCA concentrations was observed in close vicinity of spots where the highest concentration of mZVI was observed. Carbon stable isotope analysis (CSIA) yielded information on the success of the abiotic degradation of 1,1,1-TCA and indicated a heterogeneous spatio-temporal pattern of degradation. Finally, the obtained results show that mZVI slurries stabilized by guar gum can be prepared at pilot scale and directly injected into low permeable aquifers, indicating a significant removal of 1,1,1-TCA. (C) 2014 Elsevier B.V. All rights reserved.

Potassium permanganate (PM) and sodium persulfate (PS) are used in soil remediation, however, their compatibility with a coinciding or subsequent biotreatment is poorly understood. In this study, different concentrations of PM (0.005–2 g/L) and PS (0.01–4.52 g/L) were applied and their effects on the abundance, activity, and reactivation potential of a dechlorinating enrichment culture were investigated. Expression of the tceA, vcrA and 16S rRNA genes of Dehalococcoides spp. were detected at 0.005–0.01 g/L PM and 0.01–0.02 g/L PS. However, with 0.5–2 g/L PM and 1.13–4.52 g/L PS no gene expression was recorded, neither were indicator molecules for total cell activity (Adenosine triphosphate, ATP) detected. Dilution did not promote the reactivation of the microbial cells when the redox potential was above −100 mV. Similarly, inoculated cells did not dechlorinate trichloroethene (TCE) above −100 mV. When the redox potential was decreased to −300 mV and the reactors were bioaugmented for a second time, dechlorination activity recovered, but only in the reactors with 1.13 and 2.26 g/L PS. In conclusion, our results show that chemical oxidants can be combined with a biotreatment at concentrations below 0.5 g/L PM and 1 g/L PS.

International audience; Batch microcosms were setup to determine the impact of different sized zero valent iron (Fe-0) particles on microbial sulfate reduction during the in situ bio-precipitation of metals. The microcosms were constructed with aquifer sediment and groundwater from a low pH (3.1), heavy-metal contaminated aquifer. Nano (nFe(0)), micro (mFe(0)) and granular (gFe(0)) sized Fe-0 particles were added to separate microcosms. Additionally, selected microcosms were also amended with glycerol as a C-source for sulfate-reducing bacteria. In addition to metal removal, Fe-0 in microcosms also raised the pH from 3.1 to 6.5, and decreased the oxidation redox potential from initial values of 249 to 226 mV, providing more favorable conditions for microbial sulfate reduction. mFe(0) and gFe(0) in combination with glycerol were found to enhance microbial sulfate reduction. However, no sulfate reduction occurred in the controls without Fe-0 or in the microcosm amended with nFe(0). A separate dose test confirmed the inhibition for sulfate reduction in presence of nFe(0). Hydrogen produced by Fe-0 was not capable of supporting microbial sulfate reduction as a lone electron donor in this study. Microbial analysis revealed that the addition of Fe-0 and glycerol shifted the microbial community towards Desulfosporosinus sp. from a population initially dominated by low pH and metal-resisting Acidithiobacillus ferrooxidans. (C) 2013 Elsevier Ltd. All rights reserved.